One of the best places to start research is in the Five-College Library Catalog. All books are listed by their AUTHORS, TITLES, and SUBJECTS, and you can also use the KEYWORD function to search.
KEYWORD searching is not likely to yield a complete, or completely relevant, list of locally-owned books on any particular topic, but it's a good way to start; type in a common language characterization of your topic, say "darfur", select titles from the resulting list that interest you, note which official subject headings are assigned to those titles, then click on them to do a more thorough SUBJECT search.
SUBJECT searching, as such, requires that you use the exact words or phrases libraries have chosen to describe your topic; for example, libraries list books about the genocide in Darfur under "Sudan -- History -- Darfur Conflict, 2003-". Inputting that as a 'Subject begins with' search will yield the most relevant results. Ask at the Reference Desk if you're not sure what words or phrases to use.
ATLA Religion Database (1949 to present)
Index to journal articles, essays, and book reviews in the field of religion.
Historical Abstracts with Full Text (1955 to present)
Scholarly literature about world history since 1450 (excluding the United States and Canada).
Index Islamicus (1906 to present)
Covers literature on Islam, the Middle East and the Muslim world, including Muslim areas of Asia and Africa.
International Bibliography of the Social Sciences (IBSS) (1951 to present)
Indexes about 3,000 journals and 7,000 books per year.
Worldwide Political Science Abstracts (1975 to present)
Covers international journals in political science and its complementary fields.
Standard general encyclopedia.